### GTM Variable Setup Example

Source: https://context7.com/gtm-templates-knowit-experience/gtm-ga4-ecom-items-dlv-version-1-variable/llms.txt

Illustrates the configuration steps for creating a GA4 Ecommerce Items DLV Version 1 variable in GTM. Ensure to repeat this for each required ecommerce parameter.

```plaintext
Variable setup (repeat for each parameter needed):
1. Go to Variables → User-Defined Variables → New
2. Choose "GA4 Ecommerce Items Data Layer Version 1 Variable" as type
3. Set "Standard Ecommerce Parameters" to desired value (e.g., "items")
4. If selecting "items", optionally enable "Remove null or empty Values from Items"
5. Name the variable, e.g.: ecom - items - DLV - V1
6. Save
```

--------------------------------

### GA4 Ecommerce Data Layer Push Example

Source: https://context7.com/gtm-templates-knowit-experience/gtm-ga4-ecom-items-dlv-version-1-variable/llms.txt

Demonstrates a typical data layer push for GA4 ecommerce events, including clearing the previous ecommerce object and pushing a new event with item details. This example highlights how Data Layer Version 1 reads only the latest push, contrasting with Version 2's merging behavior.

```javascript
// Data layer push example (website implementation)
window.dataLayer = window.dataLayer || [];

// Step 1: Clear the ecommerce object (recommended best practice)
window.dataLayer.push({ ecommerce: null });

// Step 2: Push the ecommerce event
window.dataLayer.push({
  event: 'add_to_cart',
  ecommerce: {
    currency: 'USD',
    value: 29.99,
    coupon: 'SUMMER10',
    items: [
      {
        item_id: 'SKU_001',
        item_name: 'Blue T-Shirt',
        item_category: 'Apparel',
        price: 29.99,
        quantity: 1
      }
    ]
  }
});

// With DLV Version 1, GTM reads ONLY the above push.
// With DLV Version 2, GTM would merge with any previous ecommerce push.
// Variable configured with ecomParam = "items" returns:
// [{ item_id: 'SKU_001', item_name: 'Blue T-Shirt', item_category: 'Apparel', price: 29.99, quantity: 1 }]

// Variable configured with ecomParam = "value" returns:
// 29.99

// Variable configured with ecomParam = "coupon" returns:
// "SUMMER10"
```

--------------------------------

### GA4 Event Tag Configuration Example

Source: https://context7.com/gtm-templates-knowit-experience/gtm-ga4-ecom-items-dlv-version-1-variable/llms.txt

Shows how to integrate the custom DLV variable into a GA4 Event tag. This pattern is applicable for all standard GA4 ecommerce events.

```plaintext
GA4 Event Tag setup:
- Tag Type: Google Analytics: GA4 Event
- Event name: purchase (or add_to_cart, view_item, etc.)
- Event Parameters:
    items          → {{ecom - items - DLV - V1}}
    transaction_id → {{ecom - transaction_id - DLV - V1}}
    value          → {{ecom - value - DLV - V1}}
    currency       → (use a standard DLV for currency)
```

--------------------------------

### GA4 Ecommerce Data Layer Push with Null Values

Source: https://context7.com/gtm-templates-knowit-experience/gtm-ga4-ecom-items-dlv-version-1-variable/llms.txt

Illustrates a GA4 ecommerce data layer push containing null or empty string values within the items array. This example shows the output when the `removeNullfromItems` parameter is enabled versus disabled, demonstrating how nulls and empty strings are handled.

```javascript
// Data layer push with null values in items
window.dataLayer.push({ ecommerce: null });
window.dataLayer.push({
  event: 'purchase',
  ecommerce: {
    transaction_id: 'T_12345',
    value: 59.98,
    items: [
      {
        item_id: 'SKU_001',
        item_name: 'Blue T-Shirt',
        item_category: 'Apparel',
        item_category2: null,       // null — will become undefined and be dropped
        item_variant: '',            // empty string — will become undefined and be dropped
        price: 29.99,
        quantity: 2
      }
    ]
  }
});

// Variable configured with ecomParam = "items", removeNullfromItems = true returns:
// [
//   {
//     item_id: 'SKU_001',
//     item_name: 'Blue T-Shirt',
//     item_category: 'Apparel',
//     // item_category2 and item_variant are omitted entirely
//     price: 29.99,
//     quantity: 2
//   }
// ]

// Variable configured with ecomParam = "items", removeNullfromItems = false returns:
// [
//   {
//     item_id: 'SKU_001',
//     item_name: 'Blue T-Shirt',
//     item_category: 'Apparel',
//     item_category2: null,   // sent to GA4 as the string "null"
//     item_variant: '',
//     price: 29.99,
//     quantity: 2
//   }
// ]
```

--------------------------------

### GA4 Ecommerce Parameter Mapping

Source: https://context7.com/gtm-templates-knowit-experience/gtm-ga4-ecom-items-dlv-version-1-variable/llms.txt

Maps standard GA4 ecommerce parameter names to their corresponding data layer keys. This is useful for configuring GTM variables to read ecommerce data.

```javascript
const parameterMap = {
  'items':          'ecommerce.items',
  'item_list_id':   'ecommerce.item_list_id',
  'item_list_name': 'ecommerce.item_list_name',
  'creative_name':  'ecommerce.creative_name',
  'creative_slot':  'ecommerce.creative_slot',
  'promotion_id':   'ecommerce.promotion_id',
  'promotion_name': 'ecommerce.promotion_name',
  'location_id':    'ecommerce.location_id',
  'payment_type':   'ecommerce.payment_type',
  'shipping_tier':  'ecommerce.shipping_tier',
  'transaction_id': 'ecommerce.transaction_id',
  'affiliation':    'ecommerce.affiliation',
  'coupon':         'ecommerce.coupon',
  'value':          'ecommerce.value',
  'shipping':       'ecommerce.shipping',
  'tax':            'ecommerce.tax'
};

// GTM variable naming convention (recommended):
// {{ecom - items - DLV - V1}}
// {{ecom - transaction_id - DLV - V1}}
// {{ecom - value - DLV - V1}}

// Usage in a GA4 Event Tag (GTM Tag configuration):
// Tag Type: Google Analytics: GA4 Event
// Event Parameters:
//   items         → {{ecom - items - DLV - V1}}
//   transaction_id → {{ecom - transaction_id - DLV - V1}}
//   value          → {{ecom - value - DLV - V1}}
//   coupon         → {{ecom - coupon - DLV - V1}}
//   shipping       → {{ecom - shipping - DLV - V1}}
//   tax            → {{ecom - tax - DLV - V1}}
```

--------------------------------

### GTM Sandboxed JS for Ecommerce Data

Source: https://context7.com/gtm-templates-knowit-experience/gtm-ga4-ecom-items-dlv-version-1-variable/llms.txt

This simplified code represents the template's core logic using GTM's sandboxed `copyFromDataLayer` API. It reads the most recent ecommerce push and returns the selected parameter value.

```javascript
const dataLayer = require('copyFromDataLayer');

// Version 1 = reads only the most recently pushed value for the key
let ecom = dataLayer('ecommerce', 1);

if (ecom) {
  switch (data.ecomParam) {
    case 'transaction_id': return ecom.transaction_id;
    case 'value':          return ecom.value;
    case 'coupon':         return ecom.coupon;
    case 'shipping':       return ecom.shipping;
    case 'tax':            return ecom.tax;
    case 'payment_type':   return ecom.payment_type;
    case 'shipping_tier':  return ecom.shipping_tier;
    case 'affiliation':    return ecom.affiliation;
    // ... (all other scalar parameters)
    default:
      // ecomParam === 'items'
      ecom = ecom.items;
      if (data.removeNullfromItems && ecom) {
        ecom.forEach(function(object) {
          for (let key in object) {
            if (object[key] === null || object[key] === '') {
              object[key] = undefined; // GTM drops undefined keys
            }
          }
        });
      }
      return ecom;
  }
}

return undefined; // ecommerce key not found in data layer
```

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